In a refrigeration cycle of a vehicle cabin air conditioning apparatus of a vehicle, as a coupling provided in an solenoid clutch of a compressor compressing a refrigerant, there has been conventionally known a structure disclosed in Japanese Unexamined Utility Model Publication No. 62-167936, for example.
FIG. 8 is a cross sectional view showing an solenoid clutch using the same kind of coupling as described in the publication mentioned above by cutting along a plane passing through the axis of the solenoid clutch. In particular, as shown in FIG. 8, this kind of solenoid clutch 100 is provided with a non-rotation exciting coil 102 fixed to a housing 101, a rotor 104 arranged so as to surround the exciting coil 102, rotatably held to an axial hole tube portion 101a of the housing 101 via a bearing 103 and provided with a pulley 104a in the outer periphery, an armature 105 close to and facing to an end surface of the rotor 104, and a coupling 110 coupling the armature 105 to a rotation shaft 106 inserted to an axial hole tube portion 101a of the housing 101 so as to be movable in an axial direction.
The coupling 110 is provided with a hub 111 fitted by splines and fastened via a screw member 107 to the outer periphery of a leading end portion of the rotation shaft 106, an outer ring 112 coaxially arranged in the outer peripheral side of the hub 111, coupled to the armature 105 via a plurality of rivets 108 arranged in the circumferential direction and being a metal press formed product, and an elastic body 113 vulcanized and adhered to the opposing peripheral surfaces between the outer ring 112 and a rim portion of the hub 111 and made of an annular rubber-type elastic material.
In other words, the coupling 110 is structured such that when exciting the exciting coil 102 by energization, the coupling 110 allows the armature 105 magnetized by the exciting coil to move in an axial direction so as to be attracted to an end surface of the rotating rotor 104, on the basis of a shear deformation in an axial direction of the elastic body 113, reduces a noise at a time of the armature 105 and the rotor 104 being attracted, and transmits a torque to the rotation shaft 106 from the armature 105. Further, when the exciting coil 102 is not energized, the armature 105 is moved apart from an end surface of the rotor 104 with a slight gap G on the basis of a restoring force of the elastic body 113.
The solenoid clutch 100 generates a high heat on the basis of a friction only for a short time in the process that the armature 105 is attracted to the end surface of the rotating rotor 104. Further, in accordance with the conventional coupling 110, when the friction heat is transmitted to the outer ring 112 fastened to the armature 105, there is a risk that an adhesion portion of the elastic body 113 to the outer ring 112 is deteriorated and broken. Further, as a countermeasure thereof, there is employed a method of interposing a heat insulating spacer 109 made of a low thermal conductivity material around each of the rivets 108 and between a flange portion 112a of the outer ring 112 fastened by the rivet 108 and the armature 105, however, since an assembly becomes complicated and each of the rivets 108 still forms a heat transfer medium, it is hard to effectively prevent a heat transfer to the outer ring 112.
The present invention is made by taking the problem mentioned above into consideration, and a main technical object of the present invention is to prevent coupling breakage between an elastic body and an outer ring due to a friction heat generated by an armature and a rotor.